Singapore Quantum-Safe Handbook: What It Means for CII

Quantum-safe encryption for critical information infrastructure (CII) means protecting data in transit between sites, cloud environments and remote users with key exchange that a future quantum computer cannot break. In Singapore, the Cyber Security Agency of Singapore (CSA) Quantum-Safe Handbook is the main reference point. Operators who also run plants in Korea, Japan, India, the US or the EU have to fit its guidance alongside those jurisdictions’ timelines.

This article explains what the handbook asks of CII owners, where deadlines exist and where they do not, and how a multinational operational technology (OT) operator can build one migration plan that holds up across all of these jurisdictions.

What does Singapore’s Quantum-Safe Handbook expect from critical information infrastructure owners?

The handbook expects CII owners to treat quantum risk as a governance and planning problem now: know where your cryptography is, rank systems by how long their data stays sensitive, and build a migration roadmap. It is advisory guidance, not a new legal instrument.

The legal backdrop: the Cybersecurity Act 2018

CII owners in Singapore are regulated under the Singapore Cybersecurity Act 2018. The Act establishes a legal framework for the oversight and maintenance of national cybersecurity in Singapore, and its objectives include strengthening the protection of Critical Information Infrastructure (CII) against cyber-attacks and authorising CSA to prevent and respond to cybersecurity threats and incidents. The designated sectors are Energy, Water, Banking and Finance, Healthcare, Transport including Land, Maritime and Aviation, Infocom, Media, Security and Emergency Services and Government. Many of these run OT.

What the handbook asks for in practice

CSA developed the Quantum-Safe Handbook together with other government agencies, alongside a self-assessment Quantum Readiness Index. For a CII owner, its expectations come down to four activities:

• Governance: make a named executive responsible for quantum readiness and fund it as a programme, not as a side task for the network team.
• Cryptographic inventory: list where public-key cryptography protects CII. Look beyond IT systems to the less visible places: VPN tunnels between substations, telemetry links to a cloud historian, vendor remote-access paths and firmware-signing chains.
• Risk prioritisation: rank assets by how long their data needs to stay confidential and by how hard they are to upgrade.
• Migration and crypto agility: plan to move to standardised post-quantum algorithms, and buy equipment that lets you change algorithms without replacing hardware.

This matches the approach US agencies have taken. A joint CISA, NSA and NIST factsheet says the inventory should be led by an organization’s Information Technology (IT) and Operational Technology (OT) procurement experts, and should include engagement with supply-chain vendors.

Does Singapore set a deadline for post-quantum migration of CII?

No. Singapore has not set a statutory date by which CII must use post-quantum cryptography. The handbook encourages early action but does not impose a compliance deadline under the Cybersecurity Act 2018.

For OT, the lack of a date is a reason to start early rather than wait. CISA has noted that the dependence on industrial control systems (ICSs) is an area of concentrated vulnerability because of the long replacement life cycle of ICS hardware and wide geographic distribution of equipment. A controller bought in 2026 may still be running in 2040.

Which post-quantum algorithms has South Korea selected in its KpqC competition, and do they differ from ML-KEM?

The Korean Post-Quantum Cryptography (KpqC) Competition selected two key encapsulation mechanisms, SMAUG-T and NTRU+, and two signature schemes, HAETAE and AIMer. They are different algorithms from NIST’s ML-KEM and do not interoperate with it, even though SMAUG-T and NTRU+ are also lattice-based.

The competition ran with backing from Korean government bodies, including the National Intelligence Service (Republic of Korea), which oversees cryptographic validation for the public sector. NIST presentations now list the Korean finalists NTRU+, SMAUG-T, AIMer, HAETAE next to NIST’s own standards.

NIST’s round-one list of additional signatures includes HAETAE under Lattice-based Signatures and AIMer under Symmetric-based Signatures. AIMer’s own specification acknowledges that the signature size of AIMer is larger than NIST selected algorithms such as CRYSTALS-Dilithium. That matters for bandwidth-constrained OT links.

In practice, a gateway that negotiates ML-KEM will not interoperate with a peer that only offers SMAUG-T. If your Korean sites may face national algorithm requirements, the ability to change the post-quantum algorithm becomes a procurement requirement, not a nice-to-have.

What is Japan’s target year for migrating government and critical infrastructure systems to post-quantum cryptography?

Japan has set 2035 as its target year for migrating government systems to post-quantum cryptography, and critical infrastructure operators are expected to align with that date. This puts Japan on the same horizon as the United States.

For OT operators, the useful reading is that 2035 is when the migration should be finished, not when it should start. Moving key exchange on site-to-site links usually comes before the slower work of replacing signature schemes in device firmware and certificate hierarchies.

India: research investment first, migration guidance emerging

India approaches the issue mainly through the India National Quantum Mission, a research and capability programme, rather than a dated migration mandate. Operational guidance is starting to appear: CERT-In and SISA published Transition to Quantum Cyber Readiness in 2025, which Indian sites in a multinational group can use as their local reference.

How should multinational OT operators reconcile Asia-Pacific post-quantum guidance with NIST and EU timelines?

Use the strictest credible timeline as your outer frame, which today is NIST’s, and then sequence work by data lifetime and exposure rather than by country. Most Asia-Pacific guidance is advisory, so a single programme built around NIST milestones and algorithm agility will normally satisfy all of it.

The reference dates

Statistic: Under NIST IR 8547 (October 2026), NIST will deprecate quantum-vulnerable public-key cryptography after 2030 and disallow its use under NIST standards and guidelines after 2035.

Statistic: According to NIST (October 2026), Executive Order 14412 accelerated this timeline, requiring federal high-value assets and high-impact systems to migrate by 2030 for key establishment and 2031 for digital signatures.

Statistic: In 2024, OMB estimated the funding necessary to upgrade the government’s non-NSS IT systems to post-quantum cryptography at $7.1 billion (reported in a 2025 CRA paper). The figure shows how large the effort is even for well-funded operators.

Statistic: CISA’s 2022 assessment covered critical infrastructure systems across the 55 NCFs, the US National Critical Functions.

Statistic: In a 2023 survey of about 1,500 practitioners in the US, EU and Asia-Pacific (cited in a 2024 review), 74% are concerned about “harvest now, decrypt later” attacks. 23% of the respondents have a strategy towards post-quantum-safeness.

The EU’s Coordinated Implementation Roadmap for the transition to post-quantum cryptography follows a similar pattern: member states start early, protect high-risk use cases by around 2030, and migrate as much as feasible by 2035.

A sequencing model that works across jurisdictions

1. Start with data in transit over untrusted paths. Harvest-now-decrypt-later only works on traffic someone can record. Inter-site links over the public internet, OT-to-cloud historian feeds and vendor remote access are the most exposed, and they are also the easiest to change, because you can protect them at the network layer without touching PLCs or RTUs. CISA’s OT guidance specifically mentions multi-site operations or distributed networks wherein underlying OT systems may not use encryption.

2. Use hybrid key exchange. Combine a classical algorithm with ML-KEM so a session stays protected even if one of the two is later weakened. NIST’s draft transition guidance notes that migration may initially include hybrid solutions that incorporate the use of quantum-resistant and quantum-vulnerable algorithms. For example, Quantum Network’s QPN gateway combines a classical exchange and ML-KEM into a single session key at Layer 3, so OT devices behind it need no software changes.

3. Make algorithm agility a contract requirement. A plant in Busan and a plant in Jurong may one day need different post-quantum algorithms. Specify in procurement that the algorithm can be changed in the field, and check what happens when support ends. With QPN, for example, changing the post-quantum algorithm and receiving updates depends on an active subscription. Without one, the gateway keeps running in its current state but gets no security updates.

4. Keep legacy OT segmented while you migrate. CISA advises that entities should prioritize network segmentation for legacy OT, end-of-life software, and platforms that require extensive time to apply updates. Encrypting the links between segments and segmenting inside sites reinforce each other. Neither replaces the other.

5. Leave signatures and PKI for a second wave. Firmware signing, device certificates and code-signing chains depend on vendor roadmaps. Track them in the same inventory, but do not let them hold up protection of the links you control today.

What regulators are signalling

The tone across jurisdictions is the same: start now. In 2022, Mona Harrington, then acting Assistant Director of CISA’s National Risk Management Center, said: “Critical infrastructure and government leaders must be proactive and begin preparing for the transition to post-quantum cryptography now.” On NIST IR 8547, Dustin Moody of NIST’s Cryptographic Technology Group said “The new report can help you understand the standards and requirements of the migration”. That is why NIST’s document works as a common frame for operators who report to regulators in several countries.

For a Singapore CII owner, the practical takeaway is that the handbook sets out the method, and NIST’s dates and your Korean and Japanese obligations set the pace. Build one cryptographic inventory and one hybrid, algorithm-agile approach to network encryption. Start with the connections between sites, clouds and remote users, because that is the traffic that can be recorded today.